As characterized so far in previous posts, the scope of the Westermarck Effect seems quite narrow in that it is directly concerned only with something like sibling incest, and then only with that for siblings raised together. However, there are a number of places where Westermarck himself suggests a much more general account of what the effect named in his honour covers. At the end of ch.14 of A History of Human Marriage (all reference here to the 3rd edition) Westermarck says:
The home is kept pure from incestuous defilement neither by laws, nor by customs, nor by education, but by an instinct which under normal circumstances makes sexual love between the nearest kin a psychical impossibility. An unwritten law, says Plato, defends “as sufficiently as possible”, parents from incestuous intercourse with their children, brothers from intercourse with their sisters … ‘nor does even the desire for this intercourse come at all upon the masses’”. (Westermarck, History, p.319; bold italics mine)
While the reference to “the home”, “incestuous defilement”, and “the nearest kin” might give a reading to the first sentence that offers a gentle push towards a broader understanding of what forms of incest Westermarck’s posited instinct pertains to, the following sentence consolidates this reading, with parent and children paired up with brothers and sisters. That this is no slip, I think, is shown by a passage near the beginning of the very next chapter, one that Durham provides immediately following the gloss he gives to the Westermarck Effect in his Coevolution (p.309) that we have seen:
the existence of an innate aversion of this kind has been taken by various writers as a psychological fact proved by common experience; and it seems impossible otherwise to explain the feeling which makes the relationship between parents and children, and brothers and sisters, so free from all sexual excitement. (Westermarck History, pp. 320-321, bold italics mine)
The italics that I have added to both passages here gives the Westermarck Effect a much broader scope, applying not only to those who were in intimate contact during childhood, but to those more generally intimate while at least one of them was an infant or child.
It would be worth checking what happens to at least this latter passage in later editions–in the 5th edition, Westermarck expanded the book to 3 volumes, and discussion of incest spans 190 pages–since in his “Recent Theories of Exogamy” (Three Essays on Sex and Marriage, 1934), Westermarck notes (p.146), in responding to a criticism of Lord Raglan that his reference to “an instinctive aversion to intercourse between those who have lived together” had the “instinctive” dropped in later editions [I assume the reference here is to his 1891—but could readily be checked]; here he also underscores the “living very closely together from childhood” that Raglan omits. Westermarck’s own retrospective conclusion here on his work: “But the essence of my theory has from the beginning been the influence which close living together from childhood has exercised on the sexual instinct.” (pp.146-147)
I think that there is a genuine ambivalence in Westermarck’s writing on this. In a passage in Chapter 15 of his History that occurs between the two block quotes I have given, Westermarck says
What I maintain is, that there is an innate aversion to sexual intercourse between persons living very closely together from early youth, and that, as such persons are in most cases related, this feeling displays itself chiefly as a horror of intercourse between near kin” (p.320, ch.15 of History).
Here the reference to persons living very closely together from early youth suggests a focus on sibling incest of a certain kind. But when Westermarck opens up his discussion of this topic, in a chapter entitled “Prohibition of Marriage Between Kindred”, he begins as follows:
The horror of incest is an almost universal characteristic of mankind, the cases which seem to indicate a perfect absence of this feeling being so exceedingly rare that they must be regarded merely as anomalous aberrations from a general rule. (Westermarck, The History of Human Marriage, 3rd edition, 1901, p.290, opening of Chapter 14).
Here Westermarck immediately goes on to note that “the degrees of kinship within which intercourse is forbidden, are by no means everywhere the same”, noting that it “is most and almost universally, abominated between parents and children, especially mother and son” (p.290). However, when he returns to comment further on the “horror of incest” by saying that our feeling about incest “has all the characteristics of a real, powerful instinct, and bears evidently a close resemblance to the aversion to sexual intercourse with individuals belonging to another species.” (Westermarck, History, p.353), he is talking explicitly about “the aversion to intercourse between persons living very closely together from early youth” (loc.cit.).
So does the Westermarck Effect point to a mechanism that operates between near-age infants and children raised together, or does it identify a mechanism that leads to more widespread aversion to sexuality? Three options, with three forms of incest avoidance:
(a) sibling incest avoidance: near-age infants and children raised together
(b) offspring-to-parent incest avoidance: from infants and children to those who raise them
(c) parent-to-offspring incest avoidance: from parents to the children they raise
(a) is the view we began with; (a) + (b) is the extension of (a) that specifies a mechanism that operates via childhood experiences for later preferences w.r.t. siblings and parents; and (a)+(b)+(c) is, I think, the most natural way to read the passage above and gives us at least two mechanisms, one operating via childhood experiences (for (a) and for (b)), the other operating via adult experiences, i.e., experiences with parenting and providing care for an infant or child (for (c)). Note that the mechanism in (b) could go together with either of these, i.e., it could cover both sibs and parents as intimate associates during one’s childhood, and so hang together with (a), or it could cover both caring for and being cared for by, and so go with (c). Or it could be something separate from both, though just what, I’m not sure.
Consider how the Westermarck Effect would be modified were we to add either an offspring-to-parental incest avoidance mechanism, as in (b):
if two individuals are intimate childhood associates, having been raised together for a number of years from early in life, then those two individuals will have a psychological aversion to sexual relations to one another and/or will lack erotic feelings for one another, and will, as a result, avoid incestual behaviors with one another when they are sexually mature.
- offspring will show the same resulting aversion to any parent by whom they were raised via the same or a similar childhood association mechanism.
or a parent-to-offspring avoidance mechanism, as in (c):
- parents will show the same resulting aversion to any offspring they have raised via an attachment mechanism.
One might think that “Aha! What goes wrong in the Fritzl et al. cases is that this attachment mechanism has not ‘kicked in’, with devastating results”. But I suspect that is a hasty inference to make. For a start, a lot more is going wrong in these cases than simply an absence of sexual aversion to offspring—they involve massive deceit, physical violence, child abuse, even homicide, and all the work required to cover this up. That is, there’s a more encompassing pathology, or set of pathologies, in these cases, that don’t concern only the absence of affection and attachment. The cases that are likely to be more informative to look at here are those where the opportunity for that kind of posited attachment mechanism to kick in hasn’t been present: cases where those playing the role of parents were not presence or barely present while the children were young. Here we’d look at a subset of step-parenting and foster parenting that meets some kind of demographic constraint, as many others have done.
My gut feeling is that (b) is the least plausible inhibitory mechanism, since it supposes two things that seem questionable: (i) that teenagers and adults would otherwise have sexual desires for their parents, whereas I take there to be many other reasons to think that they would not, e.g., by the time offspring are sexually mature, the parents are significantly older, lack the same interests and sex-related lifestyles, have diminished physical features of sexual attraction; (ii) that infants and children require some inhibitory mechanism in order to avoid experiencing sexual attraction to parents later in life. Likewise, it seems likely that in the normal course of development, there are sufficient reasons for this sexual attraction to be lacking—age-related preferences, dispersal, others of sexual interest—without needing a dedicated mechanism of inhibition that is triggered through childhood experiences. The strongest potential reason to posit a (b)-like mechanism (or a (b)-like part of a mechanism) lies in the reports coming from children experiencing ARMGSA. But I haven’t seen enough of such reports, or any real attempt to analyze them, to think that these show realization of that potential yet.
While (a) is an inhibitory mechanism that takes as input early life experiences and generates as output later life preferences, desires, and behaviors, (c) is an inhibitory mechanism that takes recent and ongoing experiences in intimacy as input and generates as output constraints on preferences, desires, and behaviors at or close to that same time. (a) could take the form of imprinting, perhaps occurring during a sensitive period and perhaps mediated via parental contact, that structures the emerging sexuality of the young adult; (c) introduces adult attachment as an inhibitory mechanism on one’s already existing sexuality.